You may not need a virus scanner per se, but you sure do need to keep your system up to date and secure (good passwords and system practices - permissions etc)
Personal Anecdote: I had a debian server running, It had an uptime of 400 days and I wanted to get to 500 before restarting it to update the kernel, I was being silly, and too cocky about it being a linux system . Since it was a server that served a research group, I gave all of my coworkers an ssh account. Turns out that some hacker exploited a bad password by one of my users and loaded on automated script that ran through 5 or 6 exploits before finding one that worked (an exploit that was patched, had I updated the kernel). It rooted the server and then proceeded to set up a bot (Campus IT caught the hack before I did, they noticed suspicious IRC traffic and contacted me).
Funny story, is that I used those same scripts to take back control of the machine to backup some raw data before nuking the system.
Long story short, keep your system up to date, keep your passwords secure, maintain good administrative practices. And unless you literally go and do sudo rm -rf /* because someone online told you to, it's unlikely you will ever have any trouble with your linux computer.
